The polycarbonate of 4,4′-isopropylidenediphenol (bisphenol A polycarbonate) is a well known engineering molding plastic. Bisphenol A polycarbonate is a clear high-performance plastic having good physical properties such as dimensional stability, high heat resistance, and good impact strength. Although bisphenol-A polycarbonate has many good physical properties, its relatively high melt viscosity leads to poor melt processability and the polycarbonate exhibits poor chemical resistance.
Blends display different physical properties based upon the nature of the polymers blended together as well as the concentration of each polymer in the blend. Attempts have been made to blend bisphenol-A polycarbonate with other polymers that have good chemical resistance, processability, and machinability. These attempts to improve melt processability, chemical resistance and other physical properties of bisphenol-A polycarbonate have been made by blending bisphenol A polycarbonate with polymers such as polystyrene, elastomers, polyesters, and polyesterimides. However, blends of bisphenol-A polycarbonate with other polymeric materials have usually resulted in immiscible blend compositions. Immiscible blend compositions are inadequate for many uses because they are not clear.
Clear, miscible blends of any two polymers are rare. Differential scanning calorimetry testing detects only a single glass transition temperature (Tg) for miscible blends composed of two or more components.
There is a need in the art for visually clear or miscible, two-phase blends, which are particularly useful in applications requiring improved chemical resistance and melt processability.